WEOH07 　加速構造②　 7月31日 百周年時計台記念館 百周年記念ホール 17:50-18:10

KEKにおけるNbN多層薄膜超伝導体の下部臨界磁場測定

Lower critical field measurement of NbN multilayer thin film superconductor at KEK

○井藤 隼人（総合研究大学院大学），早野 仁司，佐伯 学行，久保 毅幸 ，片山 領（高エネルギー加速器研究機構），岩下 芳久，頓宮 拓（京都大学化学研究所），伊藤 亮平，永田 智啓（アルバック）

○Hayato Ito (SOKENDAI / KEK), Hitoshi Hayano, Takayuki Saeki, Takayuki Kubo, Ryo Katayama (KEK), Yoshihisa Iwashita, Hiromu Tongu (Kyoto ICR), Ryohei Ito, Tomohiro Nagata (ULVAC, Inc.)

A multilayer thin film structure, in which a superconductor layer (S) such as NbN and an insulating layer (I) are coated on bulk Nb (S) (S-I-S structure), has been proposed to push up the available maximum surface magnetic field of SRF cavities. By optimizing the thickness of each layer, the cavity can withstand the higher magnetic fields. It means the cavity can achieve higher accelerating field than conventional SRF cavities. In order to determine the optimum thickness of each layer and to compare the measurement results with the theoretical prediction proposed by T. Kubo, we developed the Hc1 measurement system, which can apply the AC magnetic field locally without the influence of the sample edge effects, using the third harmonic response of the applied AC magnetic field at KEK. ULVAC made the NbN-SiO2 multilayer thin film samples of various NbN thicknesses. In this report, the measurement result of the bulk Nb sample and NbN-SiO2 multilayer thin film samples of different thickness of NbN layer will be discussed.